Fat tire fun

[FirePowerMinis]

I'm planning a fat-tire "mini" and got started on some of the work for the engine.

Crappy stock manifold and reed plate.


Hopefully less-crappy version. 8 petals vs 3, streamlined intake vs the dead-end.

 

[FirePowerMinis]

Stock slug and the coated replacement. Shorter pin height to ease port timing shuffling, reduce net case volume for stuffing, etc.
I milled the booster slot and tidied up the skirt cut after pic.
I ended up roughly splitting the difference by cutting both ends of the jug.
Effectively raised ports 2mm and set quench at 1.25mm.

 

[Sprocket86]

Very interesting and what engine is this?

You seem to know your 2 cycle engine theory quite well.

Keep the posts coming!

 

[FirePowerMinis]

Very interesting and what engine is this?

You seem to know your 2 cycle engine theory quite well.

Keep the posts coming!

Thanks I tinker, and have been for a long time.

It's a Fuji/Robin as used by EZ-Go, a close cousin to the Polaris 250 2-stroke ATV, 250 Polaris Star single sled and the 400-440-488 twins that offshot. The others are all piston-port and I've been hooked on reeds for 40 years. I'm going to use a single jug from the 488 in the mini bike build, and add a cage so I can lower the jug to detune the exhaust duration without adding too much intake. Later models went to a jug-reed setup but are still iron, so I'm making my own alloy version by chopping up an old 440 Yamaha jug and hot-gluing it to the Fuji PP intake.

 

[FirePowerMinis]

I found a Yamaha 200 Blaster pipe at the scrapyard, where most of my stuff comes from, and the can from an old sled pipe.
Dimensions and torque curve were similar to what I wanted, but the bends were all wrong.
Well, I have an angle-grinder and a hot-glue machine...



Blastoid, pre-chop


Lame stock no-spansion setup